Largely, prior art search is a subjective and qualitative service. The results provided by patent search firms are weighed contextually, and the relevance assigned to any result depends from attorney to attorney. While a singular a prior art search result that covers all novel aspects is perhaps ranked higher by some, combining multiple results to target the core novelty is also a welcome practice. The technical relevancy of results is one aspect of measuring the quality provided by the prior art search firms. It is also important to ascertain how the results were identified, particularly if the search strategy was comprehensive, accurate, and the right one.
Any information retrieval context is measured on two metrics: recall and precision, and this is also applicable for patent search services. Simply put, a recall measures the quantum of relevant results retrieved for a patent search query, while precision measures the relevancy within the retrieved results. A prior art search is performed at various stages of patent life cycle, for a variety of reasons, and for differing time periods. Therefore, different prior art searches require different recall and precision and the best patent search firms understand this requirement and accordingly customize their patent retrieval approach. For example, a freedom to operate study requires a higher recall than a novelty search. The search approach customization can accordingly range from top down to bottom up and deal with the use of synonyms, performing multi generation citation search, to deciding the truncation of search terms.